It said the group targeted the synagogues because Israeli agents were working there, al-Quds editor Abdel-Bari Atwan told the BBC.

Turkish Prime Minister Recep Tayyip Erdogan, who is meeting senior ministers, said: "Our security teams, our intelligence services have to work to determine the extent of truth of the claims."

Interior Minister Abdulkadir Aksu told the Vatan newspaper that the attacks were carried out by two suicide bombers who detonated explosives as they drove past the Neve Shalom and Beth Israel synagogues.

Neve Shalom's security cameras caught one of the attackers moments before the blast, he said.

"He is in the footage, although it is not clear. We are trying to establish their identities... It is also not clear whether they were Turkish citizens or foreigners."

The Turkish authorities have also said that closed-circuit television at each synagogue filmed the licence plates of both vehicles. Their owners have been traced and are being questioned, although they have denied any involvement in the attacks.

Turkish officials have largely discounted an initial claim by a local fundamentalist group called the Islamic Front of Raiders of the Great Orient and believe instead that a major foreign organisation was responsible.

"There is no organisation in Turkey that could have carried this out by itself. It's obvious the planning was done with a foreign source," Mr Aksu was quoted as saying.

Police hope if they can identify the suicide bombers they can follow up leads and find out which group was involved.

Hard to check

On Sunday Mr Atwan told the Arabic satellite TV channel al-Jazeera that the statement was from an al-Qaeda division called Brigades of the Martyr Abu Hafz al-Masri.